Second Physics REU: Not sure if I should apply.

I'm a physics and mathematics major 1.5-2 years in to my degree and I am not sure if I should apply to some of the NSF Physics REUs. Mainly because I am not sure if I am a good candidate. I was lucky enough to get a NSF Physics REU at another University at the end of my freshman year with interesting research working with a Transmission Electron Microscope (TEM). The research which I later presented at a local regional Zone SPS Meeting. However, academically while I have nearly all "A's" I have only been going to college part time. So, I do not exactly have a whole lot of credits compared to your full time college sophomore/rising junior.

So, I am not sure if I should trouble my professors for recommendations to apply to some of these REUs since I am not sure if I am a good candidate.